Fluid fuse

ABSTRACT

A fluid fuse having an electric terminal at each end of a tubular dielectric housing, an electrically conductive member electrically connected to each of said terminals, an electrically conductive fusible element interconnecting the members, a barrier positioned adjacent to the element to separate the housing into high and low pressure chambers, and an arc extinguishing fluid, either liquid or gas, confined under pressure within the high pressure chamber. The barrier is located close enough to the element so that the heat of the arc on rupture of the fusible element will form a hole in the barrier releasing the arc extinguishing fluid to extinguish the arc between the members.

I United States Patent 1191 [11] 3,771,089

Link [4 Nov. 6, 1973 [54] FLUID FUSE FOREIGN PATENTS 0R APPLICATIONS [75] Invenm Edwin Link Waukesha, 982,012 2/l965 Great Britain 337/273 Assigneez Corporation, waukesha, 1,932,427 1/1970 Germany 337/277 [22] Filed: May 1970 Primary ExaminerBernard A. Giiheany 2 App]. 36,781 Assistant ExaminerF. E. Bell Attorney-Ronald E. Barry and James E. Nilles [52] US. Cl. 337/277, 337/204 [51] Int. Cl. H0lh 85/40 [57] ABSTRACT [58] Field of Search 337/204, 281, 277, A fluid fuse having an electric t a at each end o 337 275 239 273; 200 1 BA a tubular dielectric housing, an electrically conductive member electrically connected to each of said termi- [56] Referen e Cit d nals, an electrically conductive fusible element inter- UNITED STATES PATENTS connecting the members, a barrier positioned adjacent to the element to separate the housing into high and 799,684 9/1905 Snyder et al 337/277 X low pressure chambers and an arc extinguishing fluid 897,852 9/l908 Sachs 337/275 X h 1,462,489 7/1923 Grigsbym 337,239 e ther hquId or gas, confined under pressure wIt In t e 1,740,698 12/1929 Murrayw 337,273 hIgh pressure chamber. The barrIer 1s located close 2 3 792 940 Muller u 337/277 X enough to the element so that the heat of the arc on 2,292,058 8/1942 Crai 337/239 rupture of the fusible element will form a hole in the 2,343,422 3/1944 Rawlins 337/275 barrier releasing the arc extinguishing fluid to extin- 2,429,5l8 10/1947 Kyle et ai 337/277 uish th are between the members. 3,127,492 3/1964 Date 200/166 BA 3,268,690 8/1966 Frink et a1. 337/277 8 Chums, 2 Drawlng Figures snwsemmmwmt FLUID FUSE BACKGROUND OF THE INVENTION Fuses of the type contemplated herein are used as circuit interrupters for high voltage cables. These devices generally include a pair of conductive members connected by an elongate fusible element which ruptures in response to an overload condition setting up an arc between the conductive members. Various devices have been used to extinguish the arc on rupture of the fusible element such as gas generating sleeves which are heat activated to produce an arc suppressing atmosphere between the members. The gap between the conductive members is usually large or the conductive members are separated rapidly to aid in extinguishing the arc. Arc extinguishing gases have been used with some success as shown in the Lingal et al. US. Pat. No. 2,757,261, issued July 31, 1956, and entitled .Circuit Interrupters to extinguish the are, but have not been entirely satisfactory.

SUMMARY OF THE INVENTION The fluid fuse of this invention provides for rapid extinguishing of the are created on rupture of a fusible element through the immediate release of an arc extinguishing fluid, either liquid or gas, on rupture of the fuse. The fluid is confined under pressure on one side of a barrier which separates the fuse into high and low pressure chambers. On rupture of the fusible element, the heat of the arc will burn a hole in the barrier releasing the pressurized arc extinguishing fluid into the gap between the conductive members to extinguish the arc. The are extinguishing fluid confined within the housing can be either in the form of a dielectric liquid or gas. This arrangement provides for a non-explosive type fuse by the immediate release of an arc extinguishing fluid into the area of the are upon rupture of the fusible element. The pressure of the arc extinguishing fluid can also be used to aid in rapidly increasing the gap between theconductive members thereby increasing the length of the arc path between the conductive members.

Other objects and advantages will be apparent from the following detailed description when read-in connectionwith the accompanying drawing.

THE DRAWING FIG. 1 is a section view of one form of the invention wherein the arc extinguishing fluid,in the form of a gas,is confined under pressure within a chamber in one of the electrical members;

FIG. 2 is another form of the invention wherein an arc extinguishing fluid,in the form of a liquid,is confined within the housing under pressure.

DESCRIPTION OF THE INVENTION The fluid fuse 8 disclosed herein essentially includes a housing having a pair of. conductive members connected by means of a fusible element to form an electrihigh pressure will flow across the arc/to extinguish the arc.

Arc extinguishing fluids of the type contemplated herein may be either gas or'liquid. Any of the following fluids can be used to extinguish an arc. Sulfur hexafluoride; fluorinated hydrocarbons such as Freon; oxyfluorides such as mono-oxytetrafluoride or dioxydifluoride; carbon dioxide and insulating oils. Sulfur hexafluoride is preferred because of its stability, low condensation temperature 64 C at atmospheric pressure, and its high dielectric strength, two to four times that of air.

More specifically, and referring to FIG. 1, a fluid fuse 8 is shown which includes a tubular dielectric housing 10 having an electric terminal 12threadedly received and sealed in each end of the housing. Electrically conductive members 14 and 16 are positioned within the housing 10 and are biased by means of springs 18 and 20, respectively, for movement toward their respective terminals 12. The conductive members 14 and 16 are interconnected by means of a fusible element 22 which is designed to rupture under fault current conditions to break the circuit through the fuse 8. The conductive members 14 and 16 will normally be pulled apart by the springs 18 and 20 to draw out the arc set up on rupture of fusible element 22. In accordance with the invention, means are provided for immediately extinguishing the arc between the conductive members 14 and 16. Such means is in the form of an arc extinguishing fluid 24 confined under pressure within a wall or barrier which will burn or fuse from the heat of the arc to release the arc extinguishing fluid for flow across the gap between the conductive members.

In this regard, and referring to FIG. 1, the electric terminals 12 each include a threaded section 26 which is screwed into a threaded section 28 provided at each end of the housing 10 Seals 30 on the terminals 12'are used to seal the housing 10. The electric terminals 12 are adapted to be connected into an electric circuit in a conventional manner. The conductive members 14 and 16 are positioned within the housing and are'biased toward the adjacent terminal 12 by means of the springs 18 and 20, respectively. Electric contact between the conductive members 14 and 16 and the terminals 12 is provided by means of electrically conductive garter springs 25 positioned between the terminal 12 and the conductive members 14 and 16. The garter springs 25 also allow for the movement of the conductive members 14 and 16 into the housing terminal 12 on rupture of the fusible element 22.

The are drawn between the conductive members 14 and 16 on rupture of the fusible element 22 is immediately extinguished by the release of the arc extinguishing fluid 24. This fluid 24 is confined within a chamber 32 formed by means of the barrier or wall of the conductive member 16. The chamber 32 is filled with the arc extinguishing fluid 24 prior to assembly through an opening 44 provided at one end of the conductive member 16. The opening 44 is sealed by means ofa cap 46. On rupture of the fusible element 22, the heat of the are between the conductive members will burn a hole inthe wall of the conductive member 16, releasing the arc extinguishing fluid 24, in this case a gas, such as sulfur hexafluoride. The gas will flow through the gap between the conductive members 14 and 16 extinguishing the are before an explosive condition occurs.

Means are provided for confining the arc extinguishing fluid 24, released from the chamber 32, to the space between the ends of the conductive members 14 and 16. Such means is in the form of a pair of resilient arc chutes 38 secured to the conductive members 14 and 16. Each arc chute includes an outwardly extending flange 40 which is positioned to sealingly engage the inside walls of the tubular housing 10. The arc extinguishing fluid 24 on release from the chamber 32 will be confined in the space between the arc chutes 38. The increase in pressure in the space between the arc chutes 38 will also aid in separating the conductive members 14 and 16.

Although the chamber 32 is shown only in conductive member 16, it is also possible to include a chamber in the conductive member 14 and to confine an are extinguishing fluid in both chambers. On rupture of the fusible element, a hole will be formed in the wall of both chambers and the gas will flow across the arc gap. The are extinguishing fluid 24 could also be confined within a chamber located next to the fusible element 22 and in parallel relation thereto. On rupture of the fusible element, a hole will be burned in the wall of the chamber, releasing the arc extinguishing fluid so that it flows transversely across the arc gap.

In the embodiment shown in FIG. 2, a fluid fuse is shown wherein arc extinguishing fluid in the form of a liquid 50 such as insulating oil is used to extinguish the are. This fuse includes a tubular insulating housing 52 having threaded sections 54 at each end. One end of the housing 52 is closed by means of a cylindrical electric terminal 56 having a threaded section 58 which is screwed into one end of the housing 52. Terminal 56 is in the form of a hollow tubular member closed by a cap 61 and an end wall 60, to form a chamber 62 within the terminal 56. The wall 60 forms a barrier which separates the housing into two chambers, one chamber 62 within the terminal 56 and a second chamber 64 within the housing 52. The other end of the housing 52 is closed by means of a second tubular electric terminal 66 having a threaded section 68 which is screwed into threaded section 54 at the other end of the housing. The terminal 66 is closed by a cap 65. Both of the terminals 56 and 66 are adapted to be connected into an electric circuit.

The electric circuit across the terminals 56 and 66 is completed by means of a conductive member 70 in the form of a copper slug which is connected to the wall 60 by means of a fusible element 72 and to the terminal 66 by means of an electrically conductive winding 74 welded to the terminal 66. The copper slug is biased into the terminal 66 by means of a spring 76 secured to groove 78 provided in the slug and a groove 80 provided in the terminal 66. The spring 76 is an invertible type spring so that on release or rupture of the fusible element 72, the copper slug will be pulled into the tubular terminal 66. The heat of the are between the terminal 56 and the conductive member 70 will burn a hole in the barrier or wall 60 which will allow the arc are extinguishing insulating fluid .52 leaving a space or pocket 88 adjacent the arc chute. The pressure of the gas or air in this space or pocket 88 is higher than the pressure in the chamber 62. The pressure differential between chambers 62 and 64 is achieved by partially evacuating chamber 62 and by inserting or filling the space 88 with an inert gas or air under pressure. On rupture of the fuse 72, a hole will be burned in the wall 60 and the higher pressure air or gas in space 88 in the chamber 64 and the low pressure in chamber 62 will cause the fluid 52 in chamber 64 to flow through the hole in the barrier 60. The immediate transfer of the arc extinguishing liquid through the gap between the terminal 56 and the conductive member will extinguish the are before an explosive condition can occur. The device shown in FIG. 2 can also be used as a gas fuse by filling chamber 62 with a gas under pressure and partially evacuating chamber 64. On rupture of the fuse 72, a hole will be burned in the wall 60 allowing the gas to flow into chamber 64.

RESUME The fluid fuse of the present invention provides a non-explosive type fuse by means of the immediate transfer of an arc extinguishing fluid across the gap between the conductive members on rupture of the fuse. The are extinguishing fluid is released by using the heat of the arc to burn a hole in a barrier between two chambers in the housing. The chambers are under different pressure with the arc extinguishing fluid in the chamber of higher prssure. As soon as a hole forms in the barrier, there will be an immediate flow of arc extinguishing fluid across the gap.

I claim:

1. A fluid fuse for interrupting an electric circuit in a high voltage cable, said fuse comprising:

a housing having an electric terminal at each end 7 adapted to be connected to the electric circuit,

an electrically conductive member connected to each of said terminals and positioned within said housing, v

a fusible element connected in series with said conductive members,

a chamber within one of said members and an arc extinguishing fluid confined at high pressure within said chamber, said fluid confining members being so located that on rupture of said fusible element the heat of the arc will form a hole in said member releasing said are extinguishing fluid for transfer from the high pressure chamber into the housing and means mounted on each of said members and sealingly engaging said housing for confining said fluid to the space between said conductive members.

2. The fuse according to claim 1 wherein a high pressure chamber is provided in the other of said conductive members. I

3. The fuse according to claim 1 including means for biasing said conductive members toward said terminals to elongate said are in the space where said fluid is confined.

4. The fuse according to claim 1 wherein said fluid is sulfur hexafluoridc.

5. A non-explosive fluid fuse connected in series with a high voltage cable comprising:

an insulating sleeve,

an electrically conductive terminal sealed at each end of said sleeve,

a first electrically conductive member connectedto one of said terminals,

a second electrically conductive member connected to the other of said terminals,

a fusible element electrically connected to said members and means for forming a chamber in one of said conductive members for an arc extinguishing fluid, said chamber forming conductor being formed of a material that will fuse on subjection to the heat of the arc to release said arc extinguishing fluid and means mounted on said members and sealingly engaging said housing for confining the sulfur hexafluoride. 

1. A fluid fuse for interrupting an electric circuit in a high voltage cable, said fuse comprising: a housing having an electric terminal at each end adapted to be connected to the electric circuit, an electrically conductive member connected to each of said terminals and positioned within said housing, a fusible element connected in series with said conductive members, a chamber within one of said members and an arc extinguishing fluid confined at high pressure within said chamber, said fluid confining members being so located that on rupture of said fusible element the heat of the arc will form a hole in said member releasing said arc extinguishing fluid for transfer from the high pressure chamber into the housing and means mounted on each of said members and sealingly engaging said housing for confining said fluid to the space between said conductive members.
 2. The fuse according to claim 1 wherein a high pressure chamber is provided in the other of said conductive members.
 3. The fuse according to claim 1 including means for biasing said conductive members toward said terminals to elongate said arc in the space where said fluid is confined.
 4. The fuse according to claim 1 wherein said fluid is sulfur hexafluoride.
 5. A non-explosive fluid fuse connected in series with a high voltage cable comprising: an insulating sleeve, an electrically conductive terminal sealed at each end of said sleeve, a first electrically conductive member connected to one of said terminals, a second electrically conductive member connected to the other of said terminals, a fusible element electrically connected to said members and means for forming a chamber in one of said conductive members for an arc extinguishing fluid, said chamber forming conductor being formed of a material that will fuse on subjection to the heat of the arc to release said arc extinguishing fluid and means mounted on said members and sealingly engaging said housing for confining the fluid to the space between the conductive members.
 6. The fuse according to claim 5 wherein said confining means includes a resilient seal on both of said members positioned to sealingly engage said housing whereby said fluid is confined to the space between said sealing means on rupture of said element.
 7. The fuse according to claim 5 including means for biasing said members toward said terminals on rupture of said element.
 8. The fuse according to claim 5 wherein said fluid is sulfur hexafluoride. 